Radio systems employ different transmitters which transmit information signals to the receivers in the systems. In addition to information signals, the receivers receive different interference signals, which may include e.g. noise. The receiver always has a certain sensitivity which describes the receiver's ability of detecting signals sent by the transmitter from among noise or similar interference. Receiver sensitivity is particularly significant to succeeding of data transmission in the radio system. It is important to measure sensitivity because the sensitivity of a receiver may change due to a change in the temperature, for example. The temperature may have a considerable influence on the receiver sensitivity. The higher the quality of the components in the receiver, the smaller the influence of the temperature.
In GSM radio systems, for example, the sensitivity of a receiver, which is part of a base station, is measured by an external measurement device, which feeds a measurement signal to the receiver. From the receiver the measurement signal is connected to the transmitting end of the base station, from which the measurement signal is supplied back to the measurement device, which measures e.g. bit errors from the measurement signal. The measurement device sends measurement signals attenuated with various attenuation values to the receiver, in which case the receiver sensitivity can be determined.
The purchase price of the measurement device used in sensitivity measurement is still rather high, for which reason a measurement device is not always bought, and thus the receiver sensitivity is not measured at all. In practice, however, the receiver sensitivity is always measured one way or another because the receiver has to fulfil the sensitivity requirements set for it. In some cases deficiencies may occur in the function of a radio network if it is not checked by means of sensitivity measurement before the radio network is used that the receivers fulfil the sensitivity requirements set for them. In a prior art method sensitivity measurement requires service personnel at the location of the base station, where they measure sensitivity with a separate measurement device. The above-mentioned method is, however, slow and very laborious to implement in practice.